Conventional optical read/write pick-up mechanisms, such as those used in compact disc (“CD”) players/recorders, digital versatile disc (“DVD”) players/recorders, and the like, incorporate a relatively heavy, bulky optical read/write head attached to a tracking mechanism. Typically, both the optical read/write head and the tracking mechanism are positioned adjacent to the surface of a spinning optical storage medium, such as a CD, a DVD, or the like, during operation. This configuration is illustrated in FIG. 1. Referring to FIG. 1, the optical read/write head 10 includes a light source 12, such as a laser diode or the like, operable for transmitting encoded/un-encoded light, such as laser light or the like, to the surface 14 of the optical storage medium 16. The optical read/write head 10 also includes a light receiving device 18, such as a photodiode or the like, operable for receiving encoded/un-encoded light, such as laser light or the like, from the surface 14 of the optical storage medium 16. A reflective element 20, such as a semi-reflective mirror, a beam splitter, or the like, and a focusing lens 22 or other focusing optics may also be used to transmit the light to and/or receive the light from the surface 14 of the optical storage medium 16.
Using the optical read/write head 10, data may be retrieved from and/or stored on predetermined portions of the surface 14 of the optical storage medium 16 via the selective positioning of the tracking mechanism 24 and the optical read/write head 10. Typically, the tracking mechanism 24 includes a pick-up carrier assembly 26 movably attached to one or more guide rails 28, a portion of which may be threaded. In conjunction with a stepper motor 30 or the like, the one or more guide rails 28 are operable for moving the tracking mechanism 24 and the optical read/write head 10 linearly with respect to the surface 14 of the optical storage medium 16. Alternatively, a typical CD player/recorder may use the tracks of a CD for position control, rather than an encoder embedded in the rail, to reduce cost.
As described above, conventional optical read/write heads are relatively heavy and bulky (due to the need for a laser diode, a photodiode, focusing optics, etc.). Conventional optical read/write heads are also positioned adjacent to the surface of the optical storage medium along with a tracking mechanism. Conventional optical read/write heads are further limited to linear movement with respect to the surface of the optical storage medium. As a result, the current generation of optical read/write pick-up mechanisms has a relatively slow access time, especially when compared to that of conventional magnetic storage devices. For example, the average random access time of a CD player/recorder, a DVD player/recorder, or the like is about 100 ms. A magnetic hard drive, however, has an average random access time of about 5-10 ms. This difference in average random access time is attributable to the fact that a magnetic read/write head is relatively light and small, and may be attached to a relatively fast-moving voice coiled motor or other servo mechanism that may be moved back and forth across a magnetic platter at speeds of up to about 60 times per second. The relatively heavy, bulky optical read/write head, mounted on a linear track and controlled by a servo motor or the like, may only be moved back and forth across the optical disc at speeds of about 5-10 times per second. As a result, for many applications, a magnetic storage device is preferred. For example, many computerized game systems and the like use a magnetic storage device to run graphics-intensive applications and to store data, and an optical storage device to run other applications, such as game programs. This is due to the high speed and capacity requirements associated with such graphics and storage applications.
Recent efforts related to CD player/recorders, DVD players/recorders, and the like have focused on improving the data transfer rate by increasing the rotational speed of the spinning optical storage medium. These efforts, although marginally effective in increasing the maximum data transfer rate, do little to improve the average random access time of the drives or their capacity. Attempts to increase the capacity of optical storage media and optical storage devices have focused on combining optical and magnetic technologies. For example, “near-field recording” requires the optical read/write head to be positioned very close to the surface of the optical storage medium. Such high-density digital disc (“HDD”)-related attempts have failed due to the short working distances between the read/write head and the storage medium, contamination on the surface of the medium substantially affecting the read/write pick-up mechanism.
Thus, what is still needed is a high-speed, high-capacity optical read/write pick-up mechanism that, in various respects, may be used effectively with at least the prior two generations of optical storage media. The present invention seeks to divorce the relatively heavy, bulky portion of the optical read/write head described above from the actuation/tracking mechanism and, using free space optics and/or guided optics, replace it with a microstructure mirror, a moveable micro-electromechanical systems (“MEMS”) mirror, or the like. As a result, the weight and size of the optical read/write pick-up mechanism may be drastically reduced, especially over the surface of the optical storage medium, and the performance of the optical storage device is allowed to approach that of a magnetic storage device.
Additionally, the configuration of the optical read/write pick-up mechanism of the present invention makes it practical to read from and/or write to both surfaces of an optical storage medium, thereby increasing capacity. Finally, the use of a voice coil motor or the like, such as that used in magnetic storage devices, for the actuation and control of the reflective element makes the optical read/write pick-up mechanism of the present invention economically efficient and commercially viable.